1. Field of the Invention
The present invention relates to an oil passage arrangement in a piston for use in an engine.
2. Description of the Related Art
Conventionally, a piston pin is assembled to a piston for use in an engine for connecting a connecting rod to the piston. With a view to lubricating and cooling the piston pin, an oil passage is provided which extends from an oil ring groove formed in the piston to the interior of the piston so that a lubricating oil clinging to the inner wall of a cylinder is supplied to the piston pin. A piston provided with an oil passage as described above is represented by one disclosed in Japanese Utility Model Examined Publication No. Sho. 61-35716.
In the oil passage arrangement of the piston disclosed in the cited Publication, however, since there is provided a single oil passage extending from the oil ring groove formed in the piston to an uppermost end portion of a piston-pin hole supporting therein the piston pin, although a certain cooling effect can be expected, this means that the oil passage is formed in the piston pin supporting part which is adapted to carry a great magnitude of explosion load, and this may cause a risk of the rigidity of the piston being deteriorated. Also, the distance between the piston head part and the piston-pin hole becomes long and this causes a problem of the piston being made larger, and such a construction is not suitable for a piston head in particular for a high speed engine.